1. Field Of The Invention
The present invention relates to apparatus for measuring properties of well fluids produced from an oil or gas well at a downhole location.
2. Description Of The Prior Art
A tester valve is a valve placed downhole in a testing string of a well for selectively opening and closing the testing string to allow formation fluids to flow upward through the well. The prior art includes a number of different forms of apparatus which provide a probe which is lowered on an electric wireline into engagement with such a tester valve for operating the tester valve and for measuring properties such as pressure and temperature of the produced fluids both while the fluids are flowing and while the well is shut in. Signals from a measuring apparatus contained in the probe are transmitted up the wireline. Tester valves designed for such use are often referred to as surface read-out tester valves.
One such apparatus is disclosed in U.S. Pat. No. 4,678,035 to Goldschild which is assigned to Schlumberger Technology Corporation of Houston, Tex. The Goldschild device provides a probe suspended on a wireline, which is lowered into engagement with a tester valve for manipulating the tester valve and for measuring properties of the produced fluid. The probe of the Goldschild device latches into place within the tester valve with a pair of spring-biased latches, which are subsequently released by a cam mechanism after a predetermined number of reciprocations of the Goldschild probe relative to the tester valve.
Another such device is shown in U.S. Pat. No. 4,487,261 to Gazda which is assigned to Otis Engineering Corporation of Dallas, Tex. The Gazda probe also latches into its tester valve with a spring-loaded latch. The Gazda device, however, can be reciprocated an indeterminate number of times to open and close a tester valve which is actually contained in the probe. When it is desired to retrieve the probe and its integral tester valve, an upward pull is applied to the wireline in order to disengage the probe. The upward pull required to disengage the probe is greater than the upward pull required to move the probe between the open and closed positions of the tester valve.